Process of utilizing spent lime cooking liquors in the manufacture of paper



' e... May 13, .1930

ALBERT 1'4. CLAPP, OF DANVEBS, MASSACHUSETTS rnocnss or u'rmizme' srnnr 1.11m

ll'o Drawing.

This invention relates to a process of recovering and utilizing in the manufacture of paper spent dime cooking liquors, such as are employed for cleansing and conditloning I q 5 cellulosic materials for beating and manufacture into paper, fiberboard or the like.

In manufacturing paper from cellulosic '.fibrous materials such as manila rope, bagging, burlap, rags, cotton waste and the like, it is customary to subject such cellulosic material to the action of lime liquor at an elevated temperature and pressure in a digester. After digestion hasbcen completed, the spent liquor is se arated from the dige'stedcellu:

losic material and is wasted. Such waste liquoroften constitutes a nuisanceas .it frequently must be filtered free from lime prior to discharge and the lime sludge disposed of" independently, or Where such requirements need not be'met. it contaminates the water into which it is discharged'a'nd tendsto de-- stroy piscatorial life therein. During digestion the lime liquor reacts with and dissolves from the cellulosic material such constituents as grease, oil, lignin and siliceous inatterso-that after. digestion an appreciable 'portionl of-the limehas been spent by reaction withAhese constituents: As 1 a consequence it is ofter uneconomical'and inexped'ient to reemploy such spent liine liquor for digesting other cellulosic material,

therein. q v

p In accordance'with the processof my in-. vention I utilize such'spent' lime liquors to-I gether with the cellulosic material digested therein for the manufacture of'a waterproof, greaseproof and fireproof paper.- As disclosed and claimed in my application serial No. 94,329, filed March 12, 1926, sucha paper.

may be produced by incorporating lime either alone or in admixture with asbestos into cellulosic fiber in the beater prior to running ofi into paperzon a papermachinei The paper filled with such material is then treated with sodium silicate solution.: The solution reacts V withthe lime-to produce .a cementitious mm terial which hardens or. sets to a glass-like applicationfiled rem-nar 14, 1937. $eria1 n.- 168,225

- then charged into a rotary digester. A liquor temperature digestion.

and conditioned for beating. as the lime acts to-dissolve the siliceous and ligneous content i the digester contents onto a platform and alas the spent products would become concen-''' trated and-contaminate rather than cleanse, and condition cellulosic materialdigested L charged directly intothe beater engine as the "cellulosic materialiiis not washed free cookfme nrouoas n'r'rnn uauurac'runn or runs.

compound which imparts water, grease and fire resistivity to the paper.

In producing such. paper, in accordance with the present invention, I proceed as follows: The cellulosic material which is to be employed as a raw material for making the. paper, may be manila ',rope for example. Such rope is cut into relatively short lengths as by the use of a rag-cutter so-called, and

containing say from'5% to 20% lime based on the weight of dry fiber is then added to the digester and the charge is digested for the desired period of time and atthe desired temperature and pressure, depending'on the characteristics of the raw material and the extent of conditioning which it is desired to effect. Thus, the charge may be digested from'four totwenty-ifour hours at from fifteen to eighty pounds steam pressure,a long we "high-temperature digestion better conditioning the raw material than a short low- Asa result of digestion, the fiber cleansed of-the rope'as well as foreign material such asoil, gum and grease and to soften and open up the fiber so that it responds more readilyto'hydration. In lieu-of discharging n lowing. the liquor to drain into sewersor dis: charge basins as usual, inaccordance with myfprocess the *digester contents are disthe' calcium constituent of the spentliquor is in a form whichreadily un'ites with sodium silicate-solution to produce the cementitious material hereinbefore described. 1 Moreover,'.

from lime in the beater engine as usually done by a revolving screen washer placedithereinL The heater charge is beaten out-for the'de sired period of time, say from five to six hours, diluted to the proper consistency,- run off on a paperfi'machine lute-paper, and the paper dried. The dry paper is treated with sodium silicate'as by passing it through a solution of say about 20 Baumtoefiect its complete penetrationor treated to produce a penetration of its surface portion only, as described in my application Serial No. 168,224, filed Feb. 14, 1927, and is then dried. Reaction takes place between the lime or calcium constituent and the sodium silicate to produce a cementitious material which upon drying sets to a glasslike compound which imparts water, grease, and fire resistivity tothe paper. The sodium silicate apparently also reacts with the calcium compounds formed during digest-ion owing to its afiinity for-the calcium and sets free various filling and cementitious material in situ in the paper to produce an intimate bonding together of the fibers. The present process thus makes possible the production of papers and boards having the properties of greaseproofness, waterproofness and fireproofness by an economical method utilizing calcium constituent in a form which has heretofore been wasted. By my process, also, it is expedient to condition for beating cellulosic material such as waste paper, kraft, sulphite and other pulps by digestion in lime liquor, as

the lime content of the spent liquor is incorporated into the paper.

Having thus described an embodiment of this invention it is obvious that changes and modifications might be made therein without departing from its spirit or scope as defined by the appended claims.

I do not herein claim broadly the treatment 7 of paper filled with a material capable of reacting with sodium silicate solution to produce plastic setting compounds in situ' in the paper, as this subject matter is disclosed and claimed in my application Serial No. 94,329,

- filed March 12,1926.

Iclaim:

1. A process which comprises beating cellulosic fibrous material in the presence of spent lime cooking liquor, running the beaten material off on a paper machine, and treating the paper with sodium silicate solution.

2. A process which comprises adding spent lime cooking liquor to cellulosic fibrous material, beating the material in such spent liquor, running the beaten material off on a paper machine, and treating the paper with sodium sillcate solution.

3. A process which comprises digesting cellulosic fibrous material in lime liquor, beatmg the digested material in the spent liquor of dlgestion, runningthe beaten material off on a paper machine, and treating the paper with sodium silicate solution.

4. A process which comprises digesting cellulosic fibrous material in lime liquor, beatmg the digested material in the spent liquor of digestion, running the beaten material ofi on apaper machine, drying the paper, and treat ng the dry paper with sodium silicate solution.

' 5. A process which comprisesdigesting cellulosic fibrous material in lime liquor, beating the digested material in the spent liquor of digestion, running the beaten material ofi on a paper machine, treating the paper with sodium silicate solution, and drying the treated paper.

6. A process which comprises digesting cellulosic fibrous material at an elevated temperature and pressure in lime liquor, discharging the digested contents into a heater and beating in the presence of the spent liquor of digestion, running the beaten material off on a paper machine, treating the paper with a sodium silicate solution of about 20 Bau-In, and drying the treated paper.

7. A process which comprises beating cellulosic' fibrous material in the presence of spent lime cooking liquor, and running the beaten material associated with its cooking liquor off on a paper machine.

8. A paper filled with a substantial proportion of those calcium compounds which are produced by the digestion of cellulosic fibrous material in lime cooking liquor.

In testimony whereof I have affixed my sig- 

